#include<bits/stdc++.h>
using namespace std;
int main()
{
	double x1,x2,t,a;
	cin>>a;
	x1=a;
	do
	{
		x2=(x1+a/x1)/2;
		t=x1;
		x1=x2;
	}while(abs(x1-t)>=0.00001);
	printf("%.3f",x1);
    return 0;
}
